Garmin 723 not seeing any NMEA2000 sensors

[collinsp]

Hey Guys,

Having a problem with my new Garmin 723 which I tested on the boat this weekend. Basically I installed a new NMEA network with a Airmar 810 (temp, depth, log & heel) and an external GPS sensor GPS17x and a Digital yacht wireless module. When I check on the Garmin 723 it does not see any NMEA devices. However, when I check the Airmar on their APP all the data is there and when i remove the power to the NMEA network it drops out so I know the network is getting power and the Airmar is working. When I check Navionics via the digital yacht wireless interface I am getting location data (lat/Lon) from the Garmin GPS17x so I know that i working as well.

I have tried removing sensors one at a time to see if there is any conflict on the network and still the Garmin 723 does not see any NMEA devices?? I have read the manual and have checked everything I can but am now stumped :-(

Any advice would be welcome before I start the headache of calling Garmin :-(

Thanks

 

[neilf39]

You have got a terminator on each end of the backbone and not put a drop cable on one end? One drop cable per t-piece and plugged in to the middle of the t? Did you use any user made up connectors? Have you removed all t-pieces (except the plotter's) and plugged the backbone cables together and then introduced each t-piece one at a time to see if any particluar device on the backbone is causing a comms issue. Have you also checked the cable run lengths, total length and REN numbers are all within the NMEA 2000 limit.

 

[vas]

+1 on terminator missing! it's obvious that each device gets power as it reports on it's own means the data, so the issue is on the bus/termination

 

[collinsp]

You have got a terminator on each end of the backbone and not put a drop cable on one end? One drop cable per t-piece and plugged in to the middle of the t? Did you use any user made up connectors? Have you removed all t-pieces (except the plotter's) and plugged the backbone cables together and then introduced each t-piece one at a time to see if any particluar device on the backbone is causing a comms issue. Have you also checked the cable run lengths, total length and REN numbers are all within the NMEA 2000 limit.

Thanks for the suggestions and no terminator on the end of the backbone. The t piece is a 2 port and did use 1 made up connector as had to cut the Airmar plug off to run it through the boat, but connections looks good and will check the impedance when next at the boat. Cable lengths are are all good, nothing longer than 5M on a straight run.

 

[collinsp]

+1 on terminator missing! it's obvious that each device gets power as it reports on it's own means the data, so the issue is on the bus/termination

Will try the terminator issue and thanks for the advice

 

[vas]

no termination = the data bytes fall off in the bilge on either side

Serious no comms unless properly terminated on BOTH ends, lots of drawings on how a bus looks like and where to put the terminators.

 

[KompetentKrew]

How do you know it's "not seeing them"?

Did you go into Settings > Communications > NMEA 2000 Setup ?

Page 170 of the PDF manual.

 

[collinsp]

How do you know it's "not seeing them"?

Did you go into Settings > Communications > NMEA 2000 Setup ?

Page 170 of the PDF manual.

Yep did exactly that and nothing showing . . .

 

[Keith-i]

Seems a bit odd that the Airmar app and the DY wireless interface can see the data but not the Garmin. Sounds like a dodgy connector somewhere in the vicinity of the Garmin. Can you swap the leads around to see if this changes anything?

 

[collinsp]

Seems a bit odd that the Airmar app and the DY wireless interface can see the data but not the Garmin. Sounds like a dodgy connector somewhere in the vicinity of the Garmin. Can you swap the leads around to see if this changes anything?

Yes I thought that was odd. Did try different leads and will try the terminators when at the boat on the weekend to see if that sorts the problem. Thanks for the advice

 

[KompetentKrew]

Seems a bit odd that the Airmar app and the DY wireless interface can see the data but not the Garmin.

The Airmar 810 has bluetooth - I think that's how it's communicating when OP says they're checking it on the app.

I believe OP's diagnosis is that this shows the Airmar is getting power on the NMEA network - OP says they switch off the power to the NMEA network and the Airmar drops out. But I don't think there's evidence that data from the Airmar is reaching the rest of the NMEA 2000 network.

Are the NMEA cables handmade or moulded, @collinsp? If you're using unterminated NMEA 2000 cable and fitting the connectors yourself then the wires are quite thin and it's easy to pull one of the data wires out by twisting too much when screwing up the plug. If the power wires are intact but one of the data wires damaged then you'd see the symptoms you describe - I've done this myself. I'm not ruling out that it's the terminators though.

Otherwise I guess you know that the NMEA 2000 network should consist of a backbone that runs from front to back of the ship, and devices are connected to the backbone by drop cables. The backbone is not a single cable, but multiple lengths which are joined by T-connectors, which is where the drop cables also join the backbone. So you can fault-find each length of backbone by connecting a transducer at one end and power and an instrument at the other end (with appropriate T-connectors and terminators obviously). This is slow and a pain in the ass.

You can also test lengths of NMEA 2000 cable using a multimeter - is 12v appearing on the appropriate lines? Disconnect everything from the cable and you can check the data wires for continuity. Plug a disassembled NMEA connector into each end of the cable and then you can access the terminals more easily. Connect the blue and white wires at one end (twisting them together or using a paperclip in a disassembled NMEA connector) and then test for continuity between the blue and white at the other end.

When fitting connectors to unterminated NMEA cable I photograph the back of the connectors with my phone, because the little numbers are too small to see with the naked eye, then wire the coloured cables up according to this chart. I never remember which is male or which is female, but that's ok because the same colour always matches up with the same number on each - e.g. 2 is red, 3 is black. When taking the pic you have to hold the phone a foot or two away otherwise it won't focus, but use the editing app to zoom in and crop the edges off the pic so the back of the connector fills the whole screen. Then I always bin the photo immediately I've finished that connector, so I don't get it mixed up with the next one.

 

[KompetentKrew]

I installed a new NMEA network with a Airmar 810 (temp, depth, log & heel) and an external GPS sensor GPS17x and a Digital yacht wireless module. When I check on the Garmin 723

Out of curiosity, why the external GPS sensor?

The Garmin 723 has an internal GPS, and I would have thought that it would share this with the NMEA 2000 network (there might be a setting to enable or disable that). It's probably no problem to have two GPS sources on a network, and I don't think this is the cause of your problem - devices should be able to select which they'll use - but this seems redundant, is all.

 

[Chiara’s slave]

I had a Garmin display that I couldn’t network. Turned out it had a faulty NMEA interface. I’d have that 723 back to where it was bought, and plugged into a known working network.

 

[PaulRainbow]

I had a Garmin display that I couldn’t network. Turned out it had a faulty NMEA interface. I’d have that 723 back to where it was bought, and plugged into a known working network.

Even though the network is incorrectly installed ?

 

[Chiara’s slave]

Even though the network is incorrectly installed ?

I’m not sure it is. Though as he’s not clear about that, a 2 way T piece? It may well be incorrect.

 

[PaulRainbow]

I’m not sure it is. Though as he’s not clear about that, a 2 way T piece? It may well be incorrect.

The backbone isn't terminated at either end.

 

[KompetentKrew]

The backbone isn't terminated at either end.

Blimey! I should have read OP's comments better before replying! Of course this is the answer!

@collinsp, this PDF must be your bible: NMEA 2000 Network Fundamentals

 

[Chiara’s slave]

The backbone isn't terminated at either end.

You’re very sure. I don’t think the OP is so sure himself. Though I personally have never seen a 2 port NMEA connector so something odd is going on

 

[PaulRainbow]

You’re very sure. I don’t think the OP is so sure himself. Though I personally have never seen a 2 port NMEA connector so something odd is going on

From post #4 "Thanks for the suggestions and no terminator on the end of the backbone. The t piece is a 2 port "

From post #10 "will try the terminators when at the boat on the weekend "

Seems sure to me.

Good point on the "2 port NMEA connector" though.


@collinsp Can you confirm what you mean here ? Are you saying that you have connected two devices to a T piece ?

 

[Chiara’s slave]

I rather dismissed any comment he had on the network after the 2 port connector.

for some clarity, here’s a terminator